The present invention relates in general to flow controlling and more particularly concerns novel apparatus and techniques for controlling fluid flow, such as water in a tank or swim-in-place pool, to establish a range of relative velocities between the flowing fluid and an object in it, such as a swimmer, while the object remains substantially stationary relative to earth. An embodiment of the invention provides a compact environment for a swimmer to attain all the exercise and fun of swimming at the swimmer's pace. Thus, the invention may be said to provide the environment of a swimming pool of infinite length in a structure slightly longer and wider than a swimmer while providing a form of exercise that cannot be achieved in a conventional bounded swimming pool with stationary water.
It is known in the prior art to provide spas or tubs that create a flow through jets to allow a swimmer to swim upstream against the water jets. A difficulty with these prior art structures is that the jets create a turbulent current that often exerts sideward and up and downward forces on the swimmer and makes swimming against the longitudinal component of the current difficult. Examples of these prior devices are the swim-jet spa commercially available from Curtis Plastics of Huntington Beach, Calif., and the model AS-S1-SL3 swim spa available from Wiedemann Industries, Inc. of Muscatine, Iowa.
A search of subclasses 71 and 72 of class 272 and subclassed 488, 491 and 509 of class 4 uncovered U.S. Pat. Nos. 520,342, 1,285,259, 1,331,270, 1,630,797, 1,796,291, 1,992,891, 2,035,835 and 3,534,413.
U.S. Pat. No. 2,035,835 discloses confined flow channels in a tank; however, this patent does not disclose water driving means truly transverse to the length of the channel; therefore, the disclosed structure would create undesired turbulence. Furthermore, this patent discloses straight end walls having a tendency to create a head which would then empty wastefully into the swim channel and turbulently induce air and noise instead of contributing to establishing the desired current.
U.S. Pat. Nos. 1,285,259 and 1,331,270 disclose paddle wheels used for surface movement only and could not establish a current along the length of the channel having negligible velocity gradient along the width.
It is an important object of this invention to provide improved apparatus and techniques for flow controlling.